Tuberculosis (TB) is a disease of poverty. Ensuring access to health care without the risk of financial hardship due to out-of-pocket health care expenditures (Universal Health Coverage [UHC]) is essential for providing accessible care to underprivileged populations, but this is not enough. The End TB Strategy promotes both patient-centred TB services and social protection measures, which aim to mitigate the economic hardship faced by TB patients and their households due to direct medical and non-medical expenditures, as well as to lost income. The strategy includes a target that no families should face catastrophic total costs due to TB. The indicator linked to this target aims to capture the total economic burden linked to TB care, and thus differs from the 'catastrophic expenditure on health' indicator, a key component of the UHC monitoring framework aligned with the Sustainable Development Goals. Countries, and particularly high TB burden countries, are expected to conduct nationally representative TB patient cost surveys to establish baseline measurements for the catastrophic costs indicator. Findings from these surveys should also help identify entry points for developing policies to ensure better financial and social protection for TB patients. In this paper, we define the key measurable concepts for TB patient cost surveys, notably the types of costs that are captured, and related affordability measures. We discuss methods for measuring these notions in the UHC framework and contrast them with how they are measured in TB patient cost surveys.